3 Ways to Overcome Common Greenhouse Heating Challenges
Energy is undoubtedly one of growers’ biggest expenses. A whopping 65 to 85 percent of all energy consumed by greenhouse operations goes toward heating, according to a greenhouse energy conservation strategy bulletin produced by Michigan State University’s Erik Runkle and Rutgers University’s A.J. Both.
Problem 1: Lost Heat
Solution: Runkle and Both suggest inspecting greenhouses for leaks and patching any holes in plastic covering or side walls. In glass houses, replace any broken or missing panes. Also make sure all greenhouse doors close completely. You may want to weather-strip doors, vents and fan openings for added protection against drafts. Also consider shutting off some of your greenhouse’s exhaust fans from late fall through early spring and covering those openings with plastic.
If you want to make a greater investment in energy-savings, consider insulating side and end walls. According to Both and Runkle, the knee wall or curtain wall (often made of concrete block or brick) can be insulated to reduce heat loss.
Problem 2: Finding the Ideal Temperature
Solution: Runkle and Both recommend managing greenhouse temperatures based on specific crops and their finish dates. When greenhouses get too cold, plants will stop developing. However, overheating can lead to wasted energy. So how do you find the sweet spot (or optimum temperature) where plants will grow as fast as they can?
Researchers from Michigan State, the University of Florida and the University of Minnesota have developed a tool to help growers determine just that. The Computer Decision-Support Tool for Floriculture Crop Producers allows growers to select a specific crop and finish time at a particular temperature based on past experience, starting plant size and finished crop specifications. Then, the tool predicts the effect of increasing or decreasing temperatures in 2° F intervals.
You can also use the USDA Virtual Grower tool to predict the cost of greenhouse heating and help make decisions on temperature set points. This tool is also able to predict how much energy is needed to maintain specific temperatures at various times throughout the year.
Problem 3: Inefficient Heating Systems
If your heating system is still inefficient after a thorough tune-up, it might be worth considering an upgrade. Some of the newer, condensing boilers, for example, are highly efficient. The Infinite Energy 2 condensing boiler from Delta T Solutions offers up to 98% efficiency.
You might also consider investing in radiant bench or floor heat, such as the DELTA-TUBE™ EPDM SD rubber tube bench and DELTA-TUBE™ EPDM LD rubber tube ground heating systems. These systems heat starting at the soil level, allowing for faster germination and quicker turns. In addition, less heat is lost in the air compared to forced-air heating units, resulting in more energy dollars saved.
Source: Extension Bulletin E-3160, November 2011, Greenhouse Energy Conservation Strategies, Erik Runkle, Department of Horticulture, Michigan State University and A. J. Both, BioEnvironmental Engineering, Department of Environmental Sciences, Rutgers, The State University of New Jersey.
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